title: Aryl hydrocarbon receptor-inducible or constitutive expression of human UDP glucuronosyltransferase UGT1A6.
abstract: Transcriptional regulation of human UGT1A6, a UDP glucuronosyltransferase isoform conjugating a wide variety of planar phenols, has been studied using transfection experiments with plasmids containing its 3-kb 5' upstream region and chloramphenicol acetyltransferase as reporter gene. Previously, two modes of expression of the isoform have been described: in colon carcinoma Caco-2 cells UGT1A6 was found to be TCDD-inducible, whereas in lung carcinoma A549 cells it was constitutively expressed. Therefore functional analysis of UGT1A6 regulation was carried out using these two cell lines. In the upstream region of human UGT1A6 one xenobiotic-responsive element (XRE) was found between-1498 and -1502 bp. In Caco-2 cells the reporter gene activity of the entire plasmid and of deletion mutants containing the XRE were TCDD-inducible, in contrast to experiments with a deletion mutant which did not contain the XRE. TCDD induction was marginal in transfection studies with A549 cells. Gel mobility shift analysis indicated that the aryl hydrocarbon receptor and its partner Arnt bind to the XRE. Furthermore, primer extension studies suggest cell-specific use of multiple TATA boxes. Hence, regulation of human UGT1A6 appears to be cell-specific including both constitutive and aryl hydrocarbon receptor-controlled expression.
authors.affiliation: Institute of Toxicology, University of Tübingen, Germany.
authors.forename: P A
authors.initials: PA
authors.lastname: Münzel
authors.forename: T
authors.initials: T
authors.lastname: Lehmköster
authors.forename: M
authors.initials: M
authors.lastname: Brück
authors.forename: J K
authors.initials: JK
authors.lastname: Ritter
authors.forename: K W
authors.initials: KW
authors.lastname: Bock
mesh_terms: D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D001483:Base Sequence; D001665:Binding Sites; D002277:Carcinoma / Q000201:enzymology; D003110:Colonic Neoplasms / Q000201:enzymology; D004268:DNA-Binding Proteins; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D014453:Glucuronosyltransferase / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology; D008969:Molecular Sequence Data; D011485:Protein Binding; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012045:Regulatory Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D015398:Signal Transduction; D014018:Tissue Distribution; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
chemical_list: C497396:ARNT protein, human; D004268:DNA-Binding Proteins; D018336:Receptors, Aryl Hydrocarbon; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; C110655:UDP-glucuronosyltransferase, UGT1A6; D014453:Glucuronosyltransferase